Tuning the magnetocaloric response of Gd7-xYxPd3 (2 ≤ x ≤ 6) alloys by microstructural modifications

M Oboz,Z Śniadecki,P Zajdel

doi:10.1016/j.jmmm.2021.168829

Abstract

We investigated the influence of microstructural changes on the magnetic properties and the magnetocaloric response of the Gd7-xYxPd3 (2 ≤ x ≤ 6) alloys rapidly quenched by vacuum suction casting (rc-cast samples) and melt-spinning (melt-spun samples) techniques. Quenched-in structural disorder determines magnetic and magnetocaloric properties in both series of alloys. For the rc-cast samples two distinct magnetic transitions are visible. The peak at higher temperatures is related to the ferromagnetic/paramagnetic transition of the crystalline phase. In contrast, the peak observed at low temperatures is believed to be related to the ferro-para transition of the amorphous phase and/or a spin reorientation. The Gd7-xYxPd3 alloys in the form of rapidly cooled cast exhibit the magnetic transition temperatures at 262 K, 242 K, 202 K, 153 K and 9 K, for 2 ≤ x ≤ 6 respectively. Curie temperatures of the melt-spun Gd7-xYxPd3 alloys are much lower compared to the rc-cast samples. The melt-spun Gd5Y2Pd3 orders ferromagnetically below 90 K, while Gd4Y3Pd3, Gd3Y4Pd3, Gd2Y5Pd3 and GdY6Pd3 ribbons undergo the magnetic transformation at 65 K, 40 K, 25 K, and 9 K, respectively. Investigated ribbons exhibit almost doubled magnetic entropy change in comparison to the rc-cast samples. For instance, the -ΔSm value for melt-spun and rc-cast Gd5Y2Pd3 is equal to 6.31 Jkg-1K−1 and 3.64 Jkg-1K−1, respectively. Moreover, due to the large δTFWHM of the magnetic entropy change peak, both the melt-spun and rc-cast samples exhibit large relative cooling power (RCP), reaching 466 Jkg−1 (Δµ0H = 5 T) for the rc-cast Gd5Y2Pd3. RCP values are comparable to those of some potential magnetic refrigerants.

Highlights

In contrast to the traditional refrigeration technology of compressed gas medium, the magnetic refrigeration is an environmentally friendly technology [1, 2]
Rietveld refinement [20] was carried out using Fullprof software [21] and was performed in a way described in the previous paper [17]
The last material in the Gd7-xYxPd3 series had a different structure, which was indexed as cubic and later identified as being similar to RE5Pd2-type one [23] (marked with (II) in Fig. 1 and Table 1). The refinement of this structure was simplified by locating some atoms on positions with higher symmetry

Summary

Introduction

In contrast to the traditional refrigeration technology of compressed gas medium, the magnetic refrigeration is an environmentally friendly technology [1, 2]. Compared with the FOMT magnetocaloric materials, amorphous alloys exhibit magnetocaloric effect originating from the second order magnetic phase transition (SOMT). Such materials possess unique advantages, as for example superior mechanical properties, low hysteresis losses during magnetization, lack of thermal hysteresis, or better corrosion resistance [6,7,8]. Complex investigations of the structural, microstructural, magnetic and magnetocaloric properties of the Gd6YPd3 alloys utilizing various techniques were performed [17]. We intend to shown the influence of varied kinetics of synthesis process, utilizing different techniques, to study the impact of the microstructural changes and various degree of structural disorder on the magnetocaloric properties of the Gd7-xYxPd3 (2 ≤ x ≤ 6) alloys. The temperature dependences of magnetization were performed using a Quantum Design MPMS-XL-7AC SQUID magnetometer in the temperature range 2-400 K in magnetic fields up to 7 T

Results and discussion

Conclusions

Declaration of interests